ES2730300T3 - Pelletizing device with complementary rollers - Google Patents

Abstract

Pelletizing device comprising: - a die (11, 21, 31, 41) with a first surface, called operational surface (12, 22, 32, 42), and a second surface that is essentially parallel to the first surface (12 , 22, 32, 42), the die (11, 21, 31, 41) comprising between the first and second surfaces multiple through openings (3) for pellet formation, and - at least two rollers (14, 15; 24, 25; 34, 35; 44, 45) that can rotate around an axis, in which the rollers (14, 15; 24, 25; 34, 35; 44, 45) and the die (11, 21, 31, 41) can be moved relative to each other, each of the rollers (14, 15; 24, 25; 34, 35; 44, 45) having a surface (16, 17; 26, 27; 36, 37 ; 46, 47) operative pressing to press the material to be pelletized through the radial openings (3) of the die (11, 21, 31, 41), characterized in that a width of the surface (16, 17; 26, 27; 36, 37; 46, 47) of operative pressing in each one of the rod illos (14, 15; 24, 25; 34, 35; 44, 45) is less than a width of the operating surface (12, 22, 32, 42) of the matrix (11, 21, 31, 41) and the surface (16, 17; 26, 27; 36, 37; 46, 47) operating pressing of each of the rollers (14, 15; 24, 25; 34, 35; 44, 45) is arranged in such a way that it covers a part of the surface (12, 22, 32, 42 ) operating die (11, 21, 31, 41) which is not covered by any of the other rollers (14, 15; 24, 25; 34, 35; 44, 45).

Description

DESCRIPTION

Pelletizing device with complementary rollers

The invention relates to a pelletizing device comprising a matrix with a first surface, called the operating surface, and a second surface that is essentially parallel to the first surface, the matrix between the first and the second surface comprising multiple through openings for the pellet formation, at least two rollers that can rotate about an axis, in which the rollers and the die are movable relative to each other, each of the rollers comprising an operative pressing surface to press the pelletized material to through the radial openings of the matrix.

Products in the form of pellets are offered in many industries. These pellets have the form of large grains or small bars and are produced from fine-grained material originally. This pellet-shaped material can be easily handled, stored, packaged and transported. Examples of pellets can be found in the livestock feed industry, the recycling industry, but also in the plastics industry and the biomass industry. For example, in the wood industry, sawdust and / or wood chips are being pressed to form pellets, which can then be easily packaged and transported, but also properly dosed so that they can be fed, for example, to incinerators and boilers.

Pellet formation takes place in pelletizing devices. There are pelletizing devices in various designs. In general, all designs comprise a matrix with a first surface, called the operating surface, and a second surface that is essentially parallel to the first surface. The matrix comprises multiple through openings for pellet formation between the first and second surfaces. Pelletizing devices also comprise at least one roller that can rotate about an axis, in which the rollers and the die are movable relative to each other, each of the rollers comprising an operative pressing surface for pressing the material to pelletize through the radial openings of the matrix. There are pelletizing devices with a flat operating surface of the die and other devices have a cylindrical operating surface of the die. The one or more rollers and the die are movable with each other in such a way that the one or more rollers are passing with their operating pressure surfaces on the operating surface of the die to press the material to be pelleted, which has been placed on the surface operation of the matrix, through the openings in the matrix and thus creating the pellets. The rollers can be driven to pass over the die, but also the rollers may not be driven, but the die moves under the rollers or a combined driven motion is possible. The width of the operating pressing surface each roller is equal to or slightly greater than the width of the operating surface of the die. The roller is located at a predetermined minimum distance from the inside of the die and between the roller and the die the material to be pelleted is being compressed in the radial openings in the die. If the matrix is operated, the roller does not have to be operated separately, but instead is rotated with the rotation of the matrix and the material to be pelletized which is located between the matrix and the roller. It is also possible to have rotating rollers and stationary die. Large forces are generated during the pressing of the pellets. To generate these forces, the die or rollers are being driven with considerable power.

Within the principles described above there are still quite a few possible variants in the design of pelletizing devices. For example, a design variant can be found in the number of rollers used. One possibility is to have only one roller. However more commonly today machines are found with two or more rollers. This is mainly due to the great forces that are generated during the pressing of the pellets as mentioned above. These forces are acting on the roller and in case of a roller, the construction to keep this roller stable in these great forces can become complicated, heavy and, above all, expensive. When two rollers are being used, the construction to keep the rollers in a stable position becomes much easier. The same also happens with three or more rollers possibly to a somewhat lesser degree.

US 6 299 430 B1 describes a pelletizing device according to the preamble of claim 1.

An objective of the present invention is to provide a pelletizing device that can operate with greater efficiency.

This objective is achieved by a pelletizing device according to claim 1. Experiments have shown that a pelletizing device according to the invention uses up to 10% less energy compared to a conventional pelletizing device to produce the same. result at the same time, that is, they have the same performance per unit of time and a production of pellets of the same quality. This reduction in energy consumption is not just an advantage in terms of profitability. It opens up opportunities for the manufacture of a variety of design optimizations in pelletizing machines that cannot be performed in pelletizing machines according to the prior art. This is due to the fact that energy consumption is clearly one of the most important limiting factors in the design of pelletizing devices. Energy consumption translates directly into the heat generated by the process. Again, this determines the operating temperature of some essential parts which in turn has a great influence. about the life time of various parts. This is particularly true for the material to be pelletized with a high viscosity, such as wood chips. In this type of machines, according to the invention, it is, for example, possible to expand the width of the operating surface of the die and, therefore, increase the productivity of the machine and improve the life of the essential wear parts. Usually this can take place without changing the other dimensions of the machine.

In a pelletizing device according to claim 1 of the present invention, the operating pressing surface of each of the rollers is arranged such that it covers a portion of the operating surface of the die that is not covered by any of The other rollers. From the experiments, it is evident that the percentage of the operating surface of the die on which an operating pressing surface of more than one roller passes is inversely proportional to the reduction in energy consumption obtained by the invention.

In a preferred embodiment of the invention, the pelletizing device is arranged such that a relative movement between the die and the rollers is driven in a repetitive pattern and the operational pressing surface of each of the rollers has been established in such a way. so that during a repetitive pattern cycle at least 30% and preferably at least 90% of the operating surface of the die on which the rollers are passing only once through an operational pressing surface of a roller. In this embodiment of the invention almost all the possible increase in efficiency is realized. This condition can be fulfilled by rollers of the same length that are covering the entire width of the operating surface of the die, but where the operating pressing surface of each roller covers a different part of the width of the roller and, therefore, for Each roller this operating surface is operative in a different part of the operating surface of the die. In this case it should be clear that the operational pressing surface of a roller can comprise several parts that are separated. The alternative is to use small rollers that are being displaced relative to each other in the axial direction of the roller such that again each operating pressing surface of each roller operates on a different part of the operating surface of the die but that the surface Pressing operation on the roller itself covers essentially the entire length of the roller.

It is clear that the percentage of the operating surface of the die being pressed by a two-roller operating pressing surface must be kept to a minimum to obtain the full benefit of the reduction in energy consumption by the pelletizing device according to the invention. Ideally, this surface should be zero, however, in practice this can be difficult if not in certain cases even impossible. It is important that each of the radial openings be completely passed through at least one of the rollers. This is because if a roller passes only over part of the opening then the material to be pelletized is not being properly pressed through the opening, but the material can easily escape because a part of the opening is left free and Therefore, the pressure that is necessary to push the material through the opening is relaxing in the free part of the opening.

In cases where the openings in the die have been arranged in such a way that these openings are aligned in rows that do not overlap in the direction of the relative movement between the die and the rollers, it is quite simple to size the operational pressing surface of the rollers in such a way that the same roller passes always and always completely through all the through openings. However, when said alignment does not exist in a matrix, an optimal practice is being achieved in a pelletizing device according to claim 3 such that the areas of the cylindrical matrix surface containing the radial openings that are passed more once per revolution are sections with a width that is at least the center-to-center distance of two adjacent radial openings measured in a direction perpendicular to the relative motion of the die and the rollers. In this way it can be ensured that all radial openings are completely passed at least once per revolution of the die and that only very few through openings are only partially passed through one of the rollers which will require some energy, but not much.

In another preferred embodiment of the invention, the operating matrix surface comprises two or more spaced areas whose boundaries essentially run in the direction of relative motion. This allows the pelletizing device to be arranged in such a way that the operating pressing surfaces of the rollers in their contact with the die have a small overlap only in the space between the two or more areas of the operating surface of the die and This way achieve all the potential reduced energy consumption.

The operating roller press surfaces often comprise a specific surface structure for controlling the material during the pressing of the material through the radial openings in the die. The structure of the surface significantly reduces the movement towards the sides of the material away from the radial openings and improves the grip. In a preferred embodiment, such a surface structure comprises a pattern of parallel grooves. To increase the homogeneity of pellets, in pelletizing devices with two or more rollers according to the state of the art, each roller comprises an operating surface with a pattern that differs from the pattern of the other rollers. In this way, each time one of the rollers passes the radial opening, the material to be pelletized is pressed somewhat differently with respect to, for example, the distribution of the pressure exerted on the material to be pelleted. This advantage of a pelletizing device with two or more rollers in the case of the device according to the state of the art can also be included in a pelletizing device according to the invention by providing the operating surface on each of the rollers. with the surface structure, for example a pattern of grooves parallel to each other, however the surface structure is variable on the surface, for example, in the realization of grooves parallel to each other, the orientation of the grooves varies. In other words, it is possible, for example, to divide the circumference of the rollers into sections and change the orientation of the grooves of the grooved pattern of the operating surface in each of the sections. In this way the same advantage is achieved as with more rollers but with a different orientation of the grooves in the operating surface.

A roller that can be used in a pelletizing device according to the invention is also disclosed. The roller comprises a central line, the line around which a roller rotates during use. Being a roller with an operational pressing surface that is divided into at least two areas. Each of these areas is covering a portion of the center line of the roller, that is, a portion of the center line that is also a center line for that area. Two adjacent operative surface pressing areas are separated by a non-operative separation area also covering a portion of the center line of the roller. The total portion of the central line covered by the total operational pressing surface is less than 60% of the sum of the portions of the central line covered by all the operational pressing surface areas and separation areas. If the area of a die to be passed is divided into two lateral areas and a middle area, the roller according to claim 8 is passing over the two lateral areas. Obviously this roller is cooperating with a roller that has an operational pressing surface area, which is not claimed, since there are currently rollers in use that could be used for this purpose. However, if the total area of the matrix to be covered is divided into more than three areas, for example 5, then both rollers of a pelletizing device according to the invention are rollers according to claim 8.

The invention will be further explained below by describing a preferred embodiment of a pelletizing device according to the invention with reference to the drawings in which:

Figure 1 is a schematic view of the operating surface of the die and two rollers according to the state of the art;

Figure 2 schematic view of the operating surface of the die and two rollers in a further embodiment of a pelletizing device according to the invention;

Figure 3 schematic view of an operating surface of a die and two rollers in a second embodiment of a pelletizing device according to the invention;

Figure 4 schematic view of an operating surface of a die and two rollers in a third embodiment of a pelletizing device according to the invention;

Figure 5 schematic view of an operating surface of a die and two rollers in a fourth embodiment of a pelletizing device according to the invention; and

Figure 6 schematic perspective view of part of the circumference of a roller according to the invention.

There are pelletizing devices of various shapes and conformations and embodiments. They are composed of a matrix, with an operating surface and a second surface essentially parallel to the operating surface in which the operating surface comprises a multitude of through openings that flow into the other surface, as well as generally at least two rollers, each with an operating pressing surface that passes over the operating surface of the die. Between the die and the rollers there is pelletizing material that is pressed by the rollers when they pass over the die through the through holes of the die and are leaving at the other end as pellets. There are combinations of dies and rollers in a form of a cylindrical die and inside the cylindrical cavity the rollers are passing over the cylindrical operating surface of the die. Another embodiment is a pelletizing device with an essentially flat die usually in the form of a ring or large washer where the rollers are passing over the flat washer describing a circle whose center point coincides with the center point of the washer-shaped die . In the following examples, a die and rollers according to the state of the art are provided, as well as a die and rollers in two different embodiments according to the invention. In all cases the matrix is schematically shown as a straight flat surface, but it should be borne in mind that this is only a schematic representation and could equally well refer to a cylindrical matrix or a flat surface, the washer-shaped matrix as described above or one of any other die / roller arrangement of a pelletizing machine.

Figure 1 shows a matrix 1 with an operating surface 2 of the matrix and on the operating surface 2 a multitude of through openings 3 ending at the opposite surface of the matrix 1 not shown. The two rollers 4, 5 with their respective operative surfaces 6, 7 are also shown. The die 1 and the rollers 4, 5 according to Figure 1 represent a conventional arrangement according to the state of the art. In Figure 1, only a part of a die 1 is shown and two rollers 4, 5 are shown but it could equally well refer to an arrangement in which there are more than two rollers available. The rollers 4, 5 are making a movement with respect to the matrix 1 in which they pass on the matrix 1 in a repetitive relative movement of the 4, 5 rollers with respect to the matrix 1. The movement may be that the matrix 1 is driven and the rollers 4, 5 are stationary but passing over the surface of the die 1, or it may be that the die 1 is stationary and the rollers 4, 5 are driven and extended over the surface of the die 1 or could Be a combination of these two. The rollers 4, 5 are passing on an operative surface 2 of the matrix 1 and that on the operative surface 2 of the matrix 1 there is pelletizing material (not shown in the Figures) which has to be pressed by the rollers 4, 5 a through the openings 3 through the matrix 1 and the material comes out from the other side of the matrix 1 in the form of pellets. This operation is carried out in a continuous movement of the rollers 4, 5 on the surface 2 of the matrix 1 and continuously new material to be pelletized is being fed on the surface 2 of the matrix 1. Also the movement of the rollers 4, 5 on matrix 1 is a repetitive motion. In the case of a cylindrical die, this movement is repeated for each roller 4, 5 each time the roller has completed a pass / revolution inside the cylinder formed by the die 1. In the case of the washer type 1 die flat, for example, the movement of the rollers 4, 5 on the die 1 is repeated again in each revolution, but then the revolution is not around the cylinder, but the revolution is of the rollers around the center point of the die 1 washer-shaped when the rollers have reached their initial position again.

The rollers 4, 5 of Figure 1 according to the prior art have a respective operating pressing surface 6, 7, whose width is equal to or slightly greater than the width of the operating surface 2 of the die 1. This means that during each revolution the operating surface 2 of the mold matrix 1 is passed twice, once on the operating surface 6 of the roller 4 and the second time on the operating surface 7 of the roller 5.

Figure 2 is a schematic view of an operating surface 12 of a die 11 and two rollers 14, 15 in a first embodiment of a pelletizing device according to the invention. Matrix 11 of the pelletizing device according to the invention of Figure 2 is similar to matrix 1 of the state of the art of Figure 1. However, rollers 14, 15 with their respective operative pressing surfaces 16, 17 , are different in that the operating pressing surface 16 of the roller 14 passes over a different part of the operating surface 12 of the die 11 compared to the operating surface 17 of the roller 15. Therefore, in the pelletizing device according to the invention in this embodiment, one of the operative pressing surfaces 16, 17 of the respective rollers 14, 15 passes over each part of the operating surface 12 of the die 11 only once during a revolution of the relative repetitive motion. It is precisely this effect that causes the reduction in energy consumption of the pelletizing device according to the invention with respect to the pelletizing device according to the state of the art. It should be noted here that in the example given in Figure 2 of an embodiment of a pelletizing device according to the invention a maximum possible saving in energy consumption is being achieved by the fact that the entire operating surface 12 of the matrix 11 is passed only once during a repetitive movement cycle. In practice, it can happen that the operative pressing surfaces 16, 17 of the rollers 14, 15 are chosen such that the part of the operating surfaces 12 of the die 11 on which they are passing are slightly overlapping. Advantages of the invention are obtained from the point where the overlap is less than 100%. And the benefits increase with the reduction of overlap. Not in all cases, it will be possible to reduce an overlap to 0%. With a linear relationship between the benefit and the reduction of the overlap, the benefit of the invention is substantial when the overlap falls below 70%. This may be the case in which the openings 13 through the matrix 11 are arranged in such a way that they are not aligned but that each row of openings is offset with respect to the next row. In that case, it is necessary to have an overlap in such a way that at least all the through openings 3 of the die 11 are being completely passed through at least one of the operative pressing surfaces 16, 17 of the respective rollers 14, 15. It should also be clear that configurations that have greater overlap also continue to benefit, since they still have reduced energy consumption and, therefore, continue to fall within the protection of inventions as defined in the claims.

Figure 3 shows a schematic view of a second embodiment of a pelletizing device according to the invention. The die 21 with the operative surface 22 and the through openings 3 are similar to the dies 1, 11 of Figures 1 and 2. The rollers 24, 25 of the embodiment shown in Figure 3 are different from the rollers 14, 15 shown in Figure 2 in which the rollers 24, 25 are smaller, but have a respective operating pressing surface 26, 27 covering more or less the entire width of the roller 24, 25. The result is the same in that, in principle , an operating pressing surface 26, 27 of the respective rollers 24, 25 passes over each part of the operating surface 22 of the die 21 only once during a cycle of repetitive motion. If the arrangement of the through openings 3 in the matrix 21 so requires, also the rollers 24, 25 can be superimposed on the area of the operating surface 22 over which both pass.

Figures 4 and 5 show, respectively, the third and fourth embodiments of pelletizing devices according to the invention in which the rollers have shapes similar to those of the rollers of the first and second embodiments shown, respectively, in Figures 2 and 3, but matrices 31, 41 of the third and fourth embodiments as shown respectively in Figures 4 and 5 are different from matrices 11 and 21 shown respectively in Figures 2 and 3. The difference is that The operating surface 32, 42 of the matrices 31, 41 is being divided and separated by a small area that is not part of an operating surface. This small band of non-operational surface between two areas of the respective operating surface 32, 42 that of matrix 31, 41 is an area where the overlapping takes place between the operating pressing surfaces 36, 37, 46, 47 of the rollers 34, 35, 44, 45.

Figure 6 shows a part of a roller 14, 15, 24, 25, 34, 35, 44, 45 carrying the surface 16, 17, 26, 27, 36, 37, 46, 47 of operative pressing according to the invention in a perspective view. Normally the rollers of pelletizing devices do not exhibit a specific surface structure on their operative pressing surface. The structure is designed to reduce the movement towards the sides of the material away from the radial openings and improve the grip. To increase the homogeneity of the pellets, in pelletizing devices with two or more rollers according to the state of the art, each roller comprises a surface structure operating with a pattern that differs from the patterns of the other rollers, this to avoid 'groove formation' and to increase the homogeneity of the pellets produced. To obtain the same effect on pelletizing devices according to the invention, the rollers of these devices have their operating pressing surface divided into two or more areas in the rolling direction, the areas have different surface structures. Preferably, the areas are chosen so that with each successive repetitive movement each area of the matrix's operating surface is passed through a different surface area of the roller compared to the previous passes. In Figure 6 two such segments 8, 9 with the surface structure have been shown. In the example shown, the structure comprises a pattern of grooves parallel to each other, however, the orientation of the grooves differs from segment 8 to segment 9. In this way the same advantage is achieved as with more rollers but each with a structure surface different from the operating pressing surface.

List of reference numbers

1, 11, 21, 31, 41 Matrix

2, 12, 22, 32, 42 Matrix operating surface

3 Matrix openings

4, 14, 24, 34, 44 Roller

5, 15, 25, 35, 45 Roller

6, 16, 26, 36, 46 Roller operating pressing surface * 4

7, 17, 27, 37, 47 Roller operating pressing surface * 5

8, 9 Segments of the operating pressing surface

Claims (7)

1. Pelletizing device comprising: - a matrix (11, 21, 31, 41) with a first surface, called operating surface (12, 22, 32, 42), and a second surface that is essentially parallel to the first surface (12, 22, 32, 42 ), the matrix (11, 21, 31, 41) comprising between the first and second surface multiple openings (3) for pellet formation, and - at least two rollers (14, 15; 24, 25; 34, 35; 44, 45) that can rotate about an axis, in which the rollers (14, 15; 24, 25; 34, 35; 44, 45) and the die (11, 21, 31, 41) can be moved relative to each other, each of the rollers (14, 15; 24, 25; 34, 35; 44, 45) comprising a surface (16 , 17; 26, 27; 36, 37; 46, 47) of operative pressing to press the material to pelletize through the radial openings (3) of the die (11, 21, 31, 41), characterized in that a surface width (16, 17; 26, 27; 36, 37; 46, 47) of operative pressing on each of the rollers (14, 15; 24, 25; 34, 35; 44, 45) it is less than a width of the operating surface (12, 22, 32, 42) of the matrix (11, 21, 31, 41) and the surface (16, 17; 26, 27; 36, 37; 46, 47) of operative pressing of each of the rollers (14, 15; 24, 25; 34, 35; 44, 45) is arranged in such a way that it covers a part of the operative surface (12, 22, 32, 42) of the die (11, 21, 31, 41) that is not covered by any of the other rollers (14, 15; 24, 25; 34, 35; 44, 45). 2. Pelletizing device according to claim 1, wherein the device is arranged such that during the operation a relative movement between the rollers (14, 15; 24, 25; 34, 35; 44, 45) and The die (11, 21, 31, 41) is operated in a repetitive pattern, characterized in that the operating pressing surface (16, 17; 26, 27; 36, 37; 46, 47) of each of the rollers (14 , 15; 24, 25; 34, 35; 44, 45) has been arranged such that during a repetitive pattern cycle, a pressing surface (16, 17; 26, 27; 36, 37; 46, 47) operating of a roller (14, 15; 24, 25; 34, 35; 44, 45) passes over at least 30% and preferably at least 90% of the surface (12, 22, 32, 42) operating the matrix (11, 21, 31, 41) only once. 3. Pelletizing device according to claim 1 or 2, characterized in that the operating surface areas (12, 22, 32, 42) of the matrix that are being passed more than once per cycle are areas with a width that amount to the center-to-center distance of two adjacent radial openings (3), measured in a direction perpendicular to the direction of relative motion between the rollers (14, 15; 24, 25; 34, 35; 44, 45) and the matrix (11, 21, 31, 41). 4. Pelletizing device according to claim 1 or 2, characterized in that the operating surface (12, 22, 32, 42) of the matrix is distributed over a plurality of separate areas whose limits essentially run in the direction of relative motion between the rollers (14, 15; 24, 25; 34, 35; 44, 45) and the die (11, 21, 31, 41). 5. Pelletizing device of one of claims 1 to 4, characterized in that the operating pressing surface (16, 17; 26, 27; 36, 37; 46, 47) of each of the rollers (14, 15; 24 , 25; 34, 35; 44, 45) is distributed over the circumference in the areas (8, 9) which has a different surface structure. 6. Pelletizing device according to claim 5, characterized in that the areas (8, 9) having a different surface structure are the areas (8, 9) comprising mutually parallel grooves whose orientation differs between areas (8, 9) adjacent. 7. Pelletizing device according to claim 5 or 6, characterized in that the areas (8, 9) having a different surface structure have been arranged such that in two successive passes each part of the surface (12, 22, 32, 42) matrix operation is passed through a different area (8, 9).